Washington’s motto as “The Evergreen State” applies not just to an abundance of ever-green coniferous trees but also to the state’s school districts, which almost never identify low-performing employees. In a new Education Sector report released last week, I show that across all Washington school districts, only a miniscule number of employees were deemed unsatisfactory: 0.92 percent of teachers, 1.42 percent of principals, 1.02 percent of superintendents, and 2.1 percent of school support staff like janitors and librarians. Out of 2,251 Washington schools, 1,905 failed to identify a single low-performing teacher, and 239 out of 261 districts could not identify a single low-performing principal.

Parts of this story have been told before, starting with TNTP’s 2009 Widget Effect report and since replicated in Florida and Tennessee. Beyond adding another state to the list, my paper uses a unique dataset to add some new elements to the story. For example, my paper is the first to include not just teachers but also principals, superintendents, and support staff like librarians and janitors. The data show that districts have trouble evaluating their employees across the board, not just teachers.

In addition, I had access to the actual words and terms that districts use to label their performance categories. It turns out that, like Eskimos with snow, Washington school districts can only talk about what they can see. They have about twice as many terms for positive than negative performance, because they almost never see poor performance. Districts struggle even to create labels for poor performance, let alone to place an individual employee in one of the low-performing categories.

As I articulate in the piece, if an employer can’t differentiate between their employees, they’re likely to treat them all as interchangeable widgets when it comes time to decide on how to help them improve, how much to pay them, or which ones should be retained.

I have three basic responses. One, I mostly think this question is just an abstraction at this point. School districts across the country are still primarily relying on either/or evaluation systems where all employees are rated satisfactory or unsatisfactory. And, even the places that have implemented new evaluation systems, like Florida and Tennessee, still identify 97 or 98 percent of teachers as satisfactory. Unless you think 1-2 percent of employees is the right number of low performers (which American Federation of Teachers president Randi Weingarten implies in the Times piece), we have work to do.

Two, it’s unfortunate that we aren’t asking the opposite question: How many truly excellent teachers are there? How many teachers and principals should receive extra compensation, be protected from layoffs, be given additional responsibilities, and encouraged to stay on the job? There are two ends to every distribution, but we seem to pay an inordinate amount of attention to the negative side.

Three, there is no “right” answer to this question. It should ultimately be decided by value judgments made by local communities, which should reflect their unique needs. If student performance was low and flat in certain schools, especially compared to similar students in other schools, that community might want to hold more adults accountable. If students at a particular school achieve at high levels and show strong growth, that school probably doesn’t have the same urgency around identifying poor performers.

Dana Goldstein points out that New York City has had this particular fight before, but in most districts the distribution of evaluation ratings isn’t public information, so communities by and large haven’t had this discussion yet. Until they do, and until we start seeing something approaching real differentiation, the question about the “right” number is premature.

Washington has enacted a series of legislative and regulatory reforms improving district evaluation systems. They’ve mandated that districts use four-level rating evaluation systems instead of simple either/or determinations that most districts had been using. And they’ve introduced new elements like requiring districts to use a high-quality evaluation rubric and to factor in student growth into their ratings of teachers and principals. While these are undoubtedly positive steps, the lessons of other states suggest that merely tweaking old evaluation systems is not sufficient to change a culture that doesn’t value performance.